Pressure relief valve with a spring-loaded membrane closing body

ABSTRACT

The pressure relief valve has a spring pressure-loaded diaphragm closing body ( 13 ), which in the closed position sealingly engages on a centrally positioned valve seating surface ( 10 ) surrounding a first valve opening ( 8 ). Its spring pressure loading takes place by means of a counterpressure body ( 13 ) positioned centrally over it. The valve seating surface ( 10 ) is surrounded by a channel-like valve chamber ( 11 ) in the valve housing body ( 2 ) and on which is provided on the overpressure side at least one second valve opening ( 9 ). To be able to dissipate high overpressures, the counterpressure body ( 30 ) is surrounded by a diaphragm support ring ( 17 ) held on the valve housing ( 6 ) and which has a circumferential recess ( 19 ), whose depth measured perpendicular to the diaphragm closing body ( 13 ) determines the maximum deflection of said body ( 13 ), so that when the valve is completely opened the diaphragm closing body ( 13 ) is supported in an area between the valve seating surface ( 10 ) and its outer edge.

[0001] The invention relates to a pressure relief valve with a springpressure-loaded diaphragm closing body, which in the closed positionsealingly engages on a centrally positioned valve seating surfacesurrounding a first valve opening and whose spring pressure loadingdetermining the sealing pressure takes place by means of acounterpressure body centrally arranged in the vicinity of and over thevalve seating surface, which is surrounded by a channel-like valvechamber covered by the diaphragm closing body and provided in the valvehousing body and on which on the overpressure side is provided at leastone second valve opening.

[0002] A pressure relief valve of this type is known from U.S. Pat. No.5,944,050. This valve is only suitable for relatively low pressures as aresult of the nature of the arrangement or mounting of the diaphragmclosing body. It also takes up a relatively large construction volumewith a correspondingly high thermal inertia, which has a disadvantageouseffect e.g. when used in CO₂ air conditioning systems.

[0003] U.S. Pat. No. 5,413,311 discloses a diaphragm valve, whosecounterpressure body operated by a closing piston is surrounded by aring, which engages on the diaphragm closing body, both in the closedand the opened valve position and by means of which said diaphragmclosing body is fixed in the vicinity of its outer circumference. Italso forms a stop for the maximum lifting motion of the counterpressurebody. Said stop is positioned in such a way that with the valve openedto the maximum the diaphragm closing body has a planar configuration.Consequently when engaged on the valve seating surface it is downwardlyoutwardly curved in its central area.

[0004] FR-A-26 77 425 discloses a diaphragm closing valve, which isintended to have a maximum opening cross-section. For this purpose inthe relieved state, the diaphragm closing body is upwardly and outwardlycurved away from the plane of its peripheral fixing in plate-like orstep-like manner. For closing purposes it is deformed by a closingpiston counter to its spring tension in the direction of the valveseating surface. A downward displacement of the valve seating surfaceaway from the fixing plane of the diaphragm closing member increases thespring elastic deformation of the diaphragm closing body necessary forclosing purposes. A ring surrounding the closing piston serves both tofix the diaphragm edge and as a boundary casing for the diaphragmclosing body, when the latter has its plate-like starting shape in therelieved state with the closing piston raised.

[0005] The problem of the invention is to provide a pressure reliefvalve of the aforementioned type which, in the case of an adequatelylarge opening cross-section and without overloading its diaphragmclosing body, is suitable for pressure differences of more than 150′ barbetween its inflow and outflow sides. According to a preferredembodiment it has a low thermal inertia due to its particularly compactconstruction and despite the relatively large flow cross-section, sothat it can be used with advantage, particularly in areas withpronounced temperature changes, such as e.g. during the cooling andheating operation of a CO₂ air conditioning system.

[0006] According to the invention the problem is solved in that thecounterpressure body placed over the valve seating surface or acounterpressure plate cooperating therewith is surrounded by a diaphragmsupport ring held on the valve housing and which extends radiallyoutwards from the counterpressure body over the valve chamber to theouter edge of the diaphragm closing body and above the valve chamber hasa circumferential recess, whose depth measured perpendicular to thediaphragm closing body determines the maximum deflection of thediaphragm closing body, so that when the valve is completely opened thediaphragm closing body is supported in an area between the valve seatingsurface and its outer edge.

[0007] Embodiments of the invention are described hereinafter relativeto the attached drawings, wherein show:

[0008]FIG. 1A not true-to-scale cross-section through a pressure reliefvalve in the closed position.

[0009]FIG. 2A second embodiment of a pressure relief valve according tothe invention in cross-section.

[0010]FIG. 3A larger scale detail of the cross-sectional representationof FIG. 1 in the vicinity of the diaphragm closing body when closed.

[0011]FIG. 4A representation corresponding to FIG. 3 with a diaphragmclosing body, which is curved out and raised from the valve seat.

[0012]FIG. 5A third embodiment of a pressure relief valve according tothe invention in a larger scale cross-sectional representation.

[0013]FIG. 6A fourth embodiment of a pressure relief valve according tothe invention in a larger scale partial cross-section.

[0014] The pressure relief valve 1, which is particularly suitable forthe high pressures of a CO₂ air conditioning system, preferably has aone-piece, compact housing body 2 with a base part 5 enclosing theconnecting grooves 3, 4 and a cylindrical housing wall 6 connectedthereto and which forms a cup-shaped housing area 7, into whose bottomissue a first and a second valve openings 8 and 9 of the connectinggrooves 3 and 4. The valve seating surface 10 surrounding the firstvalve opening 8 is outwardly surrounded by a flat valve chamber 11shaped in channel-like manner into said bottom and which extendsoutwards to a clamp fit surface 12, which is intended for retaining andsealing the circumferential area of a diaphragm closing body 13.

[0015] The diaphragm closing body 13 is formed by at least one planar,preferably metallic diaphragm, which in the closed position rests on aplanar valve seating surface 10 and is maintained there in the closedposition by a counterpressure body 15 transferring the closing force ofat least one spring element 14. As a result of the planar-surfacesealing contact between the preferably finely ground valve seatingsurface 10 and the metallic diaphragm of the closing body 13, associatedwith the pressure acting in this area through the counterpressure body15, a sealing effect counteracting high pressures and thermal stressesis obtained.

[0016] In order to be able to absorb the force suddenly acting on theentire free diaphragm surface and prevent an excessive deformation ofthe diaphragm closing body 13 at the time of the opening of the valveunder a high overpressure and a corresponding falling back of thecounterpressure body 15, said body 13 is supported by the support edge16 of a flat support ring 17 above the channel-like, circumferentialvalve chamber 11 and opposite the second valve opening 9 in a radiallyclosely defined area. When the valve is closed, said support edge 16 isspaced from the diaphragm closing body 13, so that it only becomesactive during the opening movement thereof. It allows the multiplecurvature of the diaphragm closing body in its position raised from thevalve seating surface 10 preventing local overstressing and illustratedin FIG. 4.

[0017] With an outer, flat clamping edge 18, the support ring 17 alsoserves as a clamping ring for retaining the edge of the diaphragmclosing body 13. Between its clamping edge 18 and its support edge 16,the support ring 17 consequently has a recess 19 defining said edges 16,18. Starting from the position according to FIG. 3, the closing bodydiaphragm 13 can deform into the recess 19, as illustrated by the largerscale representation of the opened valve in FIG. 4.

[0018] For the sealing pressing of the support ring 17 with its clampingedge 18 against the diaphragm edge there is a screw ring 20 having anexternal thread and which engages with an internal thread 21 on thehousing wall 6.

[0019] The spring pressure loading of the diaphragm closing body 13 viathe counterpressure body 15 takes place both as a result of its springcharacteristic and as a result of the limited installation heightthereof, preferably through disk springs 14 which, in the embodimentaccording to FIG. 1, surround the shaft 22 of the counterpressure body15 and are fixed between a step of the counterpressure body 15 and athreaded ring 23 screwed into the housing area 7.

[0020] The transfer of the spring tension from the spring-loadedcounterpressure body 15 to the diaphragm closing body 13 preferablytakes place by means of a counterpressure plate 24 engaging on thediaphragm closing body 13. For a uniform pressing of the diaphragmclosing body 13 against the valve seating surface 10 contact between thecounterpressure plate 24 and the counterpressure body 15 takes place bymeans of a curved surface provided on at least one of the two and whosecentre of curvature is in the axis of the first valve opening 8. In theembodiment of FIG. 1, there is a spherically curved end face 25 of thecounterpressure body 15 in pressure-transferring contact with a planarcounterpressure plate 24 engaging on the diaphragm closing body 13.However, in the embodiments of FIGS. 5 and 6 a counterpressure member 34guided in the support ring 33 is provided at its upper end with aconvex, circular symmetrical curvature 35, which is received in acorrespondingly curved, concave recess.

[0021] In the embodiment of FIG. 2 the counterpressure body 30 onlycomprises a counterpressure plate 30 and two equidirectionally arrangeddisk springs 14 are located in a recess 31 of a screw body 32determining the spring pretension. The substantially radially directedinner surface 33 of the recess 31 is inclined away from the disk springs14, so that the latter can spring from the position corresponding to thevalve closing position away from the counterpressure body 30. Thepressure action of the counterpressure body takes place by means of theinner edge of the disk springs 14 engaging thereon. The screw body 32tensioning the disk springs 14 is screwed into the screw ring 20 holdingthe support ring 17 in order to limit the valve height. The minimumheight of the counterpressure member 30 projecting only slightly overthe support ring 17 contributes to the flat construction of the valveaccording to FIG. 2.

[0022]FIGS. 5 and 6 show pressure relief valves according to theinvention with measures to avoid tensile stresses in the diaphragmclosing body 13 as a result of an inflexible clamping fit on theclamping edge 18 and which leads to a change in the valve responsepressure. Such stresses arise because the diaphragm closing body 13 isextracted somewhat from its clamping fit on the clamping edge 18 throughits bending out during the first valve opening and due to the frictionalforces in the clamping fit cannot completely slide back during thefollowing closing.

[0023] In accordance with a first measure for avoiding tensile stressesin the diaphragm closing body and in accordance with FIGS. 5 and 6, inthe vicinity of the outer diaphragm circumference or the clamping fitsurface 18 is provided an elastic sealing ring 37 e.g. in the form of anO-ring and which is enclosed in a circumferential slot 38 of the housingbody 2 and which engages under pretension on the diaphragm closing body.Such a sealing of the diaphragm closing body makes it possible toconsiderably reduce the clamping force on the clamping edge 18, so thaton opening and closing the valve the diaphragm closing body 13 canperform an adequate sliding movement in the area of its marginal seal toprevent permanent tensile stresses.

[0024] As a second, e.g. additional measure for avoiding tensilestresses in the diaphragm closing body, in the embodiment according toFIG. 6 in the latter is provided a circularly circumferential,channel-like bulge 39. The valve chamber 11 passing beneath thediaphragm closing body 13 provides a free space for the positioning ofsuch a bulge 39. In place of a channel-like bulge 39, the diaphragmclosing body 13 can have a circumferential step in a not shown manner.However, such a step in the diaphragm closing body 13 would prevent theplacing of the peripheral clamping fit surface 12 in the same plane asthe valve seating surface 10. Such circumferential bulges 39 or stepsare able to elastically absorb the tensile force resulting from theopening movement of the diaphragm closing body 13 and arising in theplane thereof, so that an extraction of the diaphragm closing body 13from its peripheral clamping fit on the clamping fit surface 12 isprevented.

1. Pressure relief valve with a spring pressure-loaded diaphragm closingbody (13), which in the closed position sealingly engages on a centrallypositioned valve seating surface (10) surrounding a first valve opening(8) and whose spring pressure loading determining the sealing pressuretakes place by means of a counterpressure body (15) centrally arrangedin the vicinity of and over the valve seating surface (10), which issurrounded by a channel-like valve chamber (11) covered by the diaphragmclosing body (13) and provided in the valve housing body (2) and onwhich on the overpressure side is provided at least one second valveopening (9), characterized in that the counterpressure body placed overthe valve seating surface (10) or a counterpressure plate (24)cooperating therewith is surrounded by a diaphragm support ring (17)held on the valve housing (6) and which extends radially outwards fromthe counterpressure body (150 over the valve chamber (11) to the outeredge of the diaphragm closing body (13) and above the valve chamber (11)has a circumferential recess (19), whose depth measured perpendicular tothe diaphragm closing body (13) determines the maximum deflection of thediaphragm closing body (13), so that when the valve is completely openedthe diaphragm closing body (13) is supported in an area between thevalve seating surface (10) and its outer edge.
 2. Pressure relief valveaccording to claim 1, characterized in that the recess (19) is boundedradially inwards by a downwardly projecting support edge (16). 3.Pressure relief valve according to claim 1 or 2, characterized in thatthe diaphragm closing body (13) is relieved in the closed position andplanar and the valve seating surface (10) extends parallel to thediaphragm closing body (13) in the closed position.
 4. Pressure reliefvalve according to claim 2 or 3, characterized in that a counterpressureplate (24) is located between the counterpressure body (15) and thediaphragm closing body (13) and the contact between the counterpressureplate (24) and the counterpressure body (15) takes place by means of acircular symmetrical, curved surface (25) provided on at least one ofthese and whose centre of curvature is in the axis of the first valveopening (8).
 5. Pressure relief valve according to one of the claims 1to 4, characterized in that on its outer circumference the support ring(17) has a clamping edge (18) for the sealing, clamping retention of thediaphragm closing body (13) on a circumferential surface of the housingbody (2), the support ring (17) being kept under pretension by atensioning element (20) acting towards a clamping fit surface (12). 6.Pressure relief valve according to one of the claims 1 to 5,characterized in that the valve chamber (11) is radially outwardlysealed by a sealing ring (37), engaging on the diaphragm closing body(13) and located in a circumferential slot (38) of the housing body (2),so that during the opening or closing movement of the diaphragm closingbody (13) the latter performs a compensating movement in its plane inthe area of its marginal seal.
 7. Pressure relief valve according to oneof the claims 1 to 6, characterized in that in the vicinity of the valvechamber (1), the diaphragm closing body (13) has at least onechannel-like, circumferential bulge (39) or a step.
 8. Pressure reliefvalve according to one of the claims 1 to 7, characterized in that thespring pressure loading of the counterpressure body (15) is provided byat least one disk spring (14).
 9. Pressure relief valve according toclaim 8, characterized in that there are one or two equidirectionallyengaging disk springs (14), whose surface is inclined towards the firstvalve opening (8) with the valve closed.
 10. Pressure relief valveaccording to claim 8 or 9, characterized in that the counterpressurebody (13) is in the form of a plate (30) enclosed in the support ring(17).
 11. Pressure relief valve according to one of the claims 8 to 10,characterized in that the disk springs (14) are located in a recess (31)of a screw body (32) determining the spring pretension.
 12. Pressurerelief valve according to one of the claims 8 to 11, characterized inthat the screw body (32) tensioning the disk springs (14) is screwedinto the screw ring (20) retaining the support ring (17).